1. Field of the Invention
The present invention relates to a light source driving device and a method for driving a light source.
2. Description of the Related Art
Among known dimming methods are one in which a PWM signal as a dimming instruction signal is input to a light source driving device and a light source is dimming-controlled according to its duty ratio and one in which a control signal of 0 to 10 V as a dimming instruction signal is input to a light source driving device and a light source is dimming-controlled according to its analog value.
On the other hand, in recent years, digital addressable lighting interface system (DALI system) in which DALI signals as dimming instruction signals is sent to respective light source driving devices to control them have been developed as lighting control systems mainly in Europe.
However, such light source driving devices may have problems in that the number of components increases and the devices themselves become larger in order to accommodate the above-mentioned dimming methods they may need to be equipped with dimming controllers for the respective methods and a switching means for selecting between the dimming methods.
To solve the above problems, a dimming interface circuit has been proposed which can accommodate both of a control signal of 0 to 10 V and a DALI signal by means of a single dimming controller (see, for example WO2010/062449A2).
However, in the technique disclosed in WO2010/062449A2, since the dimming controller automatically determines a control signal of 0 to 10 V a determination result “0 V” is produced if no connection is made, possibly causing an erroneous operation.